I&#39;ve got a short piece of code that originally created an **SqlDataAdapter** object over and over.

Trying to streamline my calls a little bit, I replaced the **SqlDataAdapter** with an **SqlCommand** and moved the **SqlConnection** outside of the loop.

Now, whenever I try to edit rows of data returned to my **DataTable**, I get a **ReadOnlyException** thrown that was not thrown before.

NOTE: I have a custom function that retrieves the employee&#39;s full name based on their ID. For simplicity here, I used &quot;John Doe&quot; in my example code below to demonstrate my point.

*ExampleQueryOld* works with the **SqlDataAdapter**; *ExampleQueryNew* fails with the **ReadOnlyException** whenever I try to write to an element of the **DataRow**:

 - *ExampleQueryOld*

This works and has no issues:

    public static DataTable ExampleQueryOld(string targetItem, string[] sqlQueryStrings) {
      DataTable bigTable = new DataTable();
      for (int i = 0; i &lt; sqlQueryStrings.Length; i++) {
        string sqlText = sqlQueryStrings[i];
        DataTable data = new DataTable(targetItem);
        using (SqlDataAdapter da = new SqlDataAdapter(sqlText, Global.Data.Connection)) {
          try {
            da.Fill(data);
          } catch (Exception err) {
            Global.LogError(_CODEFILE, err);
          }
        }
        int rowCount = data.Rows.Count;
        if (0 &lt; rowCount) {
          int index = data.Columns.IndexOf(GSTR.Employee);
          for (int j = 0; j &lt; rowCount; j++) {
            DataRow row = data.Rows[j];
            row[index] = &quot;John Doe&quot;; // This Version Works
          }
          bigTable.Merge(data);
        }
      }
      return bigTable;
    }

 - *ExampleQueryNew*

This example throws the ReadOnlyException:

    public static DataTable ExampleQueryNew(string targetItem, string[] sqlQueryStrings) {
      DataTable bigTable = new DataTable();
      using (SqlConnection conn = Global.Data.Connection) {
        for (int i = 0; i &lt; sqlQueryStrings.Length; i++) {
          string sqlText = sqlQueryStrings[i];
          using (SqlCommand cmd = new SqlCommand(sqlText, conn)) {
            DataTable data = new DataTable(targetItem);
            try {
              if (cmd.Connection.State == ConnectionState.Closed) {
                cmd.Connection.Open();
              }
              using (SqlDataReader reader = cmd.ExecuteReader()) {
                data.Load(reader);
              }
            } catch (Exception err) {
              Global.LogError(_CODEFILE, err);
            } finally {
              if ((cmd.Connection.State &amp; ConnectionState.Open) != 0) {
                cmd.Connection.Close();
              }
            }
            int rowCount = data.Rows.Count;
            if (0 &lt; rowCount) {
              int index = data.Columns.IndexOf(GSTR.Employee);
              for (int j = 0; j &lt; rowCount; j++) {
                DataRow row = data.Rows[j];
                try {
                  // ReadOnlyException thrown below: &quot;Column &#39;index&#39;  is read only.&quot;
                  row[index] = &quot;John Doe&quot;;
                } catch (ReadOnlyException roErr) {
                  Console.WriteLine(roErr.Message);
                }
              }
              bigTable.Merge(data);
            }
          }
        }
      }
      return bigTable;
    }

Why can I write to the **DataRow** element in one case, but not in the other?

Is it because the **SqlConnection** is still open or is the **SqlDataAdapter** doing something behind the scene?

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ReadOnlyException DataTable DataRow "Column X is read only."