How Can I Change a DataTable Column's DataType After It's Populated?

Can’t change data type? Clone DataTable and convert columns

You try to change the DataType of a DataColumn in a DataTable. Unfortunately, once a DataTable is populated with data, its DataType cannot be modified directly.

To achieve your goals, a slightly different approach is required: data cloning. Here’s how to do it:

1. Clone DataTable: Use the Clone() method to create a cloned version of the original DataTable. This creates a separate DataTable with the same structure and schema as the original table.

<code>DataTable dtCloned = dt.Clone();</code>

2. Change column type: In the cloned DataTable, you can now modify the DataType of the required columns.

<code>dtCloned.Columns[0].DataType = typeof(Int32); // 假设原始列为 Double</code>

3. Import data: Iterate over the rows of the original DataTable and import them into the clone table using the ImportRow() method. This will transfer the data with the original value, but now with a modified DataType.

<code>foreach (DataRow row in dt.Rows) 
{
    dtCloned.ImportRow(row);
}</code>

This method allows you to convert the DataType of the column after it is populated with data. Remember that the original DataTable remains unchanged and you will use the modified cloned DataTable instead.

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