// 自定义比较器类
public class MultiColumnComparer : IEqualityComparer<DataRow>
{
    public bool Equals(DataRow x, DataRow y)
    {
        // 比较多列的值
        return x["Column1"].Equals(y["Column1"]) && 
               x["Column2"].Equals(y["Column2"]) &&
               x["Column3"].Equals(y["Column3"]);
    }

    public int GetHashCode(DataRow obj)
    {
        // 组合多列的哈希码
        return obj["Column1"].GetHashCode() ^ 
               obj["Column2"].GetHashCode() ^ 
               obj["Column3"].GetHashCode();
    }
}

// 使用示例
DataTable dt = GetDataTable(); // 获取数据表
var distinctRows = dt.AsEnumerable().Distinct(new MultiColumnComparer());

DataTable dt = GetDataTable();
var distinctRows = dt.AsEnumerable()
    .GroupBy(row => new {
        Column1 = row["Column1"],
        Column2 = row["Column2"],
        Column3 = row["Column3"]
    })
    .Select(group => group.First());

DataTable dt = GetDataTable();
var distinctRows = dt.AsEnumerable()
    .Select(row => new {
        Column1 = row["Column1"],
        Column2 = row["Column2"],
        Column3 = row["Column3"]
    })
    .Distinct();

return string.Equals(x["Column1"].ToString(), y["Column1"].ToString(), StringComparison.OrdinalIgnoreCase);

DataTable result = distinctRows.CopyToDataTable();