blocks|key|894133|text|using(SqlDataReader+rdr+=+cmd.ExecuteReader())
{
++++while+(rdr.Read())
++++{
++++++++var+myString+=+rdr.GetString(0);+//The+0+stands+for+"the+0'th+column",+so+the+first+column+of+the+result.
++++++++//+Do+somthing+with+this+rows+string,+for+example+to+put+them+in+to+a+list
++++++++listDeclaredElsewhere.Add(myString);
++++}
}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|894134|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>using(SqlDataReader rdr = cmd.ExecuteReader())
{
 while (rdr.Read())
 {
 var myString = rdr.GetString(0); //The 0 stands for "the 0'th column", so the first column of the result.
 // Do somthing with this rows string, for example to put them in to a list
 listDeclaredElsewhere.Add(myString);
 }
}
</code></pre>

blocks|key|1108979|text|string+col1Value+=+rdr["ColumnOneName"].ToString();|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1108980|或|unstyled|1108981|string+col1Value+=+rdr[0].ToString();|1108982|这些是objects，所以您需要对它们进行强制转换或.ToString()。|offset|length|style|CODE|1108983|entityMap^0|0|0|0|3|6|Q|B|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@]|A|$B|C]]|$1|D|3|E|5|F|7|R|8|@]|9|@]|A|$]]|$1|G|3|H|5|6|7|S|8|@]|9|@]|A|$B|C]]|$1|I|3|J|5|F|7|T|8|@$K|U|L|V|M|N]|$K|W|L|X|M|N]]|9|@]|A|$]]|$1|O|3|-4|5|F|7|Y|8|@]|9|@]|A|$]]]|P|$]]

<pre><code>string col1Value = rdr["ColumnOneName"].ToString();
</code></pre>

or

<pre><code>string col1Value = rdr[0].ToString();
</code></pre>

These are <code>object</code>s, so you need to either cast them or <code>.ToString()</code>.

blocks|key|1109023|text|将从"ColumnName"所在的数据库返回的begin列的名称放入其中。如果是字符串，则可以使用.ToString()。如果是另一种类型，则需要使用System.Convert进行转换。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1109024|SqlDataReader+rdr+=+cmd.ExecuteReader();
while+(rdr.Read())
{
++++string+column+=+rdr["ColumnName"].ToString();
++++int+columnValue+=+Convert.ToInt32(rdr["ColumnName"]);
}|code-block|syntax|javascript|1109025|entityMap^0|2|C|1D|B|23|E|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]|$9|P|A|Q|B|C]|$9|R|A|S|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|T|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|U|8|@]|D|@]|E|$]]]|L|$]]

Put the name of the column begin returned from the database where <code>"ColumnName"</code> is. If it is a string, you can use <code>.ToString()</code>. If it is another type, you need to convert it using <code>System.Convert</code>.

<pre><code>SqlDataReader rdr = cmd.ExecuteReader();
while (rdr.Read())
{
 string column = rdr["ColumnName"].ToString();
 int columnValue = Convert.ToInt32(rdr["ColumnName"]);
}
</code></pre>

blocks|key|1109156|text|while(rdr.Read())
{
+++string+col=rdr["colName"].ToString();
}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1109157|它会起作用的|unstyled|1109158|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$B|C]]|$1|D|3|E|5|F|7|J|8|@]|9|@]|A|$]]|$1|G|3|-4|5|F|7|K|8|@]|9|@]|A|$]]]|H|$]]

<pre><code>while(rdr.Read())
{
 string col=rdr["colName"].ToString();
}
</code></pre>

it wil work

blocks|key|894374|text|对于单个结果：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|894375|if+(reader.Read())
{
++++Response.Write(reader[0].ToString());
++++Response.Write(reader[1].ToString());
}|code-block|syntax|javascript|894376|对于多个结果：|894377|while+(reader.Read())
{
++++Response.Write(reader[0].ToString());
++++Response.Write(reader[1].ToString());
}|894378|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

For a single result:

<pre><code>if (reader.Read())
{
 Response.Write(reader[0].ToString());
 Response.Write(reader[1].ToString());
}
</code></pre>

For multiple results:

<pre><code>while (reader.Read())
{
 Response.Write(reader[0].ToString());
 Response.Write(reader[1].ToString());
}
</code></pre>

blocks|key|894418|text|我想把我的helper方法分享给那些可以使用它的人：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|894419|public+static+class+Sql
{
++++public+static+T+Read<T>(DbDataReader+DataReader,+string+FieldName)
++++{
++++++++int+FieldIndex;
++++++++try+{+FieldIndex+=+DataReader.GetOrdinal(FieldName);+}
++++++++catch+{+return+default(T);+}

++++++++if+(DataReader.IsDBNull(FieldIndex))
++++++++{
++++++++++++return+default(T);
++++++++}
++++++++else
++++++++{
++++++++++++object+readData+=+DataReader.GetValue(FieldIndex);
++++++++++++if+(readData+is+T)
++++++++++++{
++++++++++++++++return+(T)readData;
++++++++++++}
++++++++++++else
++++++++++++{
++++++++++++++++try
++++++++++++++++{
++++++++++++++++++++return+(T)Convert.ChangeType(readData,+typeof(T));
++++++++++++++++}
++++++++++++++++catch+(InvalidCastException)
++++++++++++++++{
++++++++++++++++++++return+default(T);
++++++++++++++++}
++++++++++++}
++++++++}
++++}
}|code-block|syntax|javascript|894420|用法：|894421|cmd.CommandText+=+@"SELECT+DISTINCT+[SoftwareCode00],+[MachineID]+
++++++++++++++++++++FROM+[CM_S01].[dbo].[INSTALLED_SOFTWARE_DATA]";
using+(SqlDataReader+data+=+cmd.ExecuteReader())
{
++++while+(data.Read())
++++{
++++++++usedBy.Add(
++++++++++++Sql.Read<String>(data,+"SoftwareCode00"),+
++++++++++++Sql.Read<Int32>(data,+"MachineID"));
++++}
}|894422|帮助器方法转换为您喜欢的任何值，如果它不能转换或数据库值为NULL，则结果将为null。|894423|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Q|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|R|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|S|8|@]|9|@]|A|$]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

Thought to share my helper method for those who can use it:

<pre><code>public static class Sql
{
 public static T Read&lt;T&gt;(DbDataReader DataReader, string FieldName)
 {
 int FieldIndex;
 try { FieldIndex = DataReader.GetOrdinal(FieldName); }
 catch { return default(T); }

 if (DataReader.IsDBNull(FieldIndex))
 {
 return default(T);
 }
 else
 {
 object readData = DataReader.GetValue(FieldIndex);
 if (readData is T)
 {
 return (T)readData;
 }
 else
 {
 try
 {
 return (T)Convert.ChangeType(readData, typeof(T));
 }
 catch (InvalidCastException)
 {
 return default(T);
 }
 }
 }
 }
}
</code></pre>

Usage:

<pre><code>cmd.CommandText = @"SELECT DISTINCT [SoftwareCode00], [MachineID] 
 FROM [CM_S01].[dbo].[INSTALLED_SOFTWARE_DATA]";
using (SqlDataReader data = cmd.ExecuteReader())
{
 while (data.Read())
 {
 usedBy.Add(
 Sql.Read&lt;String&gt;(data, "SoftwareCode00"), 
 Sql.Read&lt;Int32&gt;(data, "MachineID"));
 }
}
</code></pre>

The helper method casts to any value you like, if it can't cast or the database value is NULL, the result will be null.

blocks|key|894256|text|实际上，我自己发现我可以做到：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|894257|while+(rdr.read())
{++
++string+str+=+rdr.GetValue().ToString().Trim();++
}|code-block|syntax|javascript|894258|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Actually, I figured it out myself that I could do this:

<pre><code>while (rdr.read())
{ 
 string str = rdr.GetValue().ToString().Trim(); 
}
</code></pre>

blocks|key|1109335|text|我知道这有点老了，但是如果你正在把一个SqlDataReader的内容读入一个类，那么这将是非常方便的。读取器和类的列名应该相同|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1109336|public+static+List<T>+Fill<T>(this+SqlDataReader+reader)+where+T+:+new()
++++++++{
++++++++++++List<T>+res+=+new+List<T>();
++++++++++++while+(reader.Read())
++++++++++++{
++++++++++++++++T+t+=+new+T();
++++++++++++++++for+(int+inc+=+0;+inc+<+reader.FieldCount;+inc%2B%2B)
++++++++++++++++{
++++++++++++++++++++Type+type+=+t.GetType();
++++++++++++++++++++string+name+=+reader.GetName(inc);
++++++++++++++++++++PropertyInfo+prop+=+type.GetProperty(name);
++++++++++++++++++++if+(prop+!=+null)
++++++++++++++++++++{
++++++++++++++++++++++++if+(name+==+prop.Name)
++++++++++++++++++++++++{
++++++++++++++++++++++++++++var+value+=+reader.GetValue(inc);
++++++++++++++++++++++++++++if+(value+!=+DBNull.Value)
++++++++++++++++++++++++++++{+
++++++++++++++++++++++++++++++++prop.SetValue(t,+Convert.ChangeType(value,+prop.PropertyType),+null);
++++++++++++++++++++++++++++}
++++++++++++++++++++++++++++//prop.SetValue(t,+value,+null);

++++++++++++++++++++++++}
++++++++++++++++++++}
++++++++++++++++}
++++++++++++++++res.Add(t);
++++++++++++}
++++++++++++reader.Close();

++++++++++++return+res;
++++++++}|code-block|syntax|javascript|1109337|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

I know this is kind of old but if you are reading the contents of a SqlDataReader into a class, then this will be very handy. the column names of reader and class should be same

<pre><code>public static List&lt;T&gt; Fill&lt;T&gt;(this SqlDataReader reader) where T : new()
 {
 List&lt;T&gt; res = new List&lt;T&gt;();
 while (reader.Read())
 {
 T t = new T();
 for (int inc = 0; inc &lt; reader.FieldCount; inc++)
 {
 Type type = t.GetType();
 string name = reader.GetName(inc);
 PropertyInfo prop = type.GetProperty(name);
 if (prop != null)
 {
 if (name == prop.Name)
 {
 var value = reader.GetValue(inc);
 if (value != DBNull.Value)
 { 
 prop.SetValue(t, Convert.ChangeType(value, prop.PropertyType), null);
 }
 //prop.SetValue(t, value, null);

 }
 }
 }
 res.Add(t);
 }
 reader.Close();

 return res;
 }
</code></pre>

blocks|key|894214|text|最简单地说，如果您的查询返回column_name，并且包含一个字符串：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|894215|while+(rdr.Read())
{
++++string+yourString+=+rdr.getString("column_name")
}|code-block|syntax|javascript|894216|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

In the simplest terms, if your query returns column_name and it holds a string:

<pre><code>while (rdr.Read())
{
 string yourString = rdr.getString("column_name")
}
</code></pre>

blocks|key|894535|text|我通常以这种方式通过数据读取器读取数据。只是添加了一个小示例。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|894536|string+connectionString+=+"Data+Source=DESKTOP-2EV7CF4;Initial+Catalog=TestDB;User+ID=sa;Password=tintin11#";
string+queryString+=+"Select+*+from+EMP";

using+(SqlConnection+connection+=+new+SqlConnection(connectionString))
using+(SqlCommand+command+=+new+SqlCommand(queryString,+connection))
++++++++++++{
++++++++++++++++connection.Open();

++++++++++++++++using+(SqlDataReader+reader+=+command.ExecuteReader())
++++++++++++++++{
++++++++++++++++++++if+(reader.HasRows)
++++++++++++++++++++{
++++++++++++++++++++++++while+(reader.Read())
++++++++++++++++++++++++{
++++++++++++++++++++++++++++Console.WriteLine(String.Format("{0},+{1}",+reader[0],+reader[1]));
++++++++++++++++++++++++}
++++++++++++++++++++}
++++++++++++++++++++reader.Close();
++++++++++++++++}
++++++++++++}|code-block|syntax|javascript|894537|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

I usually read data by data reader this way. just added a small example.

<pre><code>string connectionString = "Data Source=DESKTOP-2EV7CF4;Initial Catalog=TestDB;User ID=sa;Password=tintin11#";
string queryString = "Select * from EMP";

using (SqlConnection connection = new SqlConnection(connectionString))
using (SqlCommand command = new SqlCommand(queryString, connection))
 {
 connection.Open();

 using (SqlDataReader reader = command.ExecuteReader())
 {
 if (reader.HasRows)
 {
 while (reader.Read())
 {
 Console.WriteLine(String.Format("{0}, {1}", reader[0], reader[1]));
 }
 }
 reader.Close();
 }
 }
</code></pre>

blocks|key|894343|text|我有一个助手函数，如下所示：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|894344|++public+static+string+GetString(object+o)
++++{
++++++++if+(o+==+DBNull.Value)
++++++++++++return+"";

++++++++return+o.ToString();
++++}|code-block|syntax|javascript|894345|然后我使用它来提取字符串：|894346|+tbUserName.Text+=+GetString(reader["UserName"]);|894347|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

I have a helper function like:

<pre><code> public static string GetString(object o)
 {
 if (o == DBNull.Value)
 return "";

 return o.ToString();
 }
</code></pre>

then I use it to extract the string:

<pre><code> tbUserName.Text = GetString(reader["UserName"]);
</code></pre>

blocks|key|1109400|text|你必须在这里read+database+column。你可以看看下面的代码片段|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1109401|++++++++++++++++string+connectionString+=+ConfigurationManager.ConnectionStrings["NameOfYourSqlConnectionString"].ConnectionString;
++++++++++++++++using+(var+_connection+=+new+SqlConnection(connectionString))
++++++++++++++++{
++++++++++++++++++++_connection.Open();

++++++++++++++++++++using+(SqlCommand+command+=+new+SqlCommand("SELECT+SomeColumnName+FROM+TableName",+_connection))
++++++++++++++++++++{

++++++++++++++++++++++++SqlDataReader+sqlDataReader+=+command.ExecuteReader();
++++++++++++++++++++++++if+(sqlDataReader.HasRows)
++++++++++++++++++++++++{
++++++++++++++++++++++++++++while+(sqlDataReader.Read())
++++++++++++++++++++++++++++{
++++++++++++++++++++++++++++++++string+YourFirstDataBaseTableColumn+=+sqlDataReader["SomeColumn"].ToString();+//+Remember+Type+Casting+is+required+here+it+has+to+be+according+to+database+column+data+type
++++++++++++++++++++++++++++++++string+YourSecondDataBaseTableColumn+=+sqlDataReader["SomeColumn"].ToString();
++++++++++++++++++++++++++++++++string+YourThridDataBaseTableColumn+=+sqlDataReader["SomeColumn"].ToString();

++++++++++++++++++++++++++++}
++++++++++++++++++++++++}
++++++++++++++++++++++++sqlDataReader.Close();
++++++++++++++++++++}
++++++++++++++++++++_connection.Close();|code-block|syntax|javascript|1109402|entityMap^0|6|4|B|F|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]|$9|P|A|Q|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|R|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|S|8|@]|D|@]|E|$]]]|L|$]]

You have to <code>read</code> <code>database column</code>here. You could have a look on following code snippet 

<pre><code> string connectionString = ConfigurationManager.ConnectionStrings["NameOfYourSqlConnectionString"].ConnectionString;
 using (var _connection = new SqlConnection(connectionString))
 {
 _connection.Open();

 using (SqlCommand command = new SqlCommand("SELECT SomeColumnName FROM TableName", _connection))
 {

 SqlDataReader sqlDataReader = command.ExecuteReader();
 if (sqlDataReader.HasRows)
 {
 while (sqlDataReader.Read())
 {
 string YourFirstDataBaseTableColumn = sqlDataReader["SomeColumn"].ToString(); // Remember Type Casting is required here it has to be according to database column data type
 string YourSecondDataBaseTableColumn = sqlDataReader["SomeColumn"].ToString();
 string YourThridDataBaseTableColumn = sqlDataReader["SomeColumn"].ToString();

 }
 }
 sqlDataReader.Close();
 }
 _connection.Close();
</code></pre>

I have a SQL Server 2008 database and I am working on it in the backend. I am working on asp.net/C#

<pre><code>SqlDataReader rdr = cmd.ExecuteReader(); 
while (rdr.Read()) 
{ 
 //how do I read strings here???? 
} 
</code></pre>

I know that the reader has values. My SQL command is to select just 1 column from a table. The column contains strings ONLY. I want to read the strings (rows) in the reader one by one. How do I do this?

Read data from SqlDataReader

SQL Server

数据库

我有一个SQL Server 2008数据库，我正在后端处理它。我正在研究asp.net/C#。SqlDataReader rdr = cmd.ExecuteReader();  while (rdr.Read())  {                 //how do I read strings here????  }  我知道读者是有价值观的。我的SQL命令是从一个表中只选择一列。该列仅包

问从SqlDataReader读取数据
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回答 12

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